Automatic electrical re-winding system for clockwork mechanisms, especially in railroad engine speed-recorders



March 29, 1966 J. E. CASTILLE AUTOMATIC ELECTRICAL RE-WINDING SYSTEM FOR CLOCKWORK MECHANISMS, ESPECIALLY IN RAILROAD ENGINE SPEED-RECORDERS Filed June 12, 1964 2 Sheets-Sheet 1 March 29, 1966 s-n 3,242,663

AUTOMATIC ELECTRICAL RE-WINDING SYSTEM FOR CLOCKWORK MECHANISMS, ESPECIALLY IN RAILROAD v ENGINE SPEED-RECORDERS Filed June 12, 1964 2 Sheets-Sheet 2 jive/171M lrri/mw United States Patent AUTOMATIC ELECTRICAL RE-WINDING SYSTEM FOR CLOCKWORK MECHANISMS, ESPECIALLY IN RAILROAD ENGINE SPEED-RECORDERS Jules E. Castille, Paris, France, assignor to Ateliers Vaucanson, Paris, France, a company of France Filed June 12, 1964, Ser. No. 374,694 Claims priority, application France, July 2, 1963, 940,079 12 Claims. (Cl. 58-41) Tachometer or speed-recording devices, as provided e.g. on railroad engines, generally-include a clockwork mechanism for controlling the timing of the cyclic functions cooperating in the measuring process. Such clockwork mechanism usually takes the form of a spring-drum assembly having an output gear which actuates a pinion secured on the shaft of an escapement wheel, which shaft also carries cams arranged to control the said cyclic functions.

The escapement wheel is rotated stepwise in angular increments and cooperates with a reciprocating balancewheel for controlling the regular timing of the angular increments or steps thereof. The reciprocatory motion of the balance wheel is sustained by means of an anchor, which in turn cooperates with the escapement wheel to control the angular steps thereof on the one hand, and on the other hand to receive actuating pulses therefrom which serve to sustain the reciprocation of the balancewheel.

Thus the impulse imparted by the anchor to the balance wheel is related to the motor torque of the escapement wheel, that is the torsion of the power spring of the spring-drum assembly. The strength of said impulse should be maintained within a range determined by the construction of the escapement system, but, with all other factors remaining equal, it is evident that the uniformity of the impulse with time will be the greater, as the drive torque of the escapement wheel, i.e. the torsion of the power hairspring of the spring-drum unit, is subjected to a smaller degree of variation over its operating cycle. It is accordingly desirable that the hairspring should be wound up by small amounts but at frequent intervals, i.e. that the spring be wound frequently a limited number of turns each time.

In a recording tachometer, the re-winding of the hairspring must be performed automatically without involving any manual operation. It is necessary moreover that the rewinding operations should be so performed as to enable all displacements of the vehicle to be recorded in order to provide a complete record thereof. This requires that the escapement shall operate before or at the latest at the very beginning of any displacement of the vehicle.

Present-day railroad engines, provided with electric or diesel-electric power plants, are equipped with electric storage batteries serving to power ancillary equipment thereon such as the starting motor, pantograph raising motor, lighting system and the like. Such storage batteries deliver a voltage output which varies considerably in service, e.g. over a range from 45 to 90 volts. It would be advantageous to use the current output from such ancillary storage batteries for the automatic re-winding of the spring-drum driving the tachometer clockwork movement, and such re-winding operations should of course have to be effected as soon as the ancillary power circuit is placed under voltage.

Now, whenever the current in the ancillary power supply circuits has been cut off for a relatively long period of time, since re-winding operations are no longer effected, the spring-drum unit will give up the power stored in its hairspring to the output gear of the unit, and when this power has been exhausted the output gear will stop. It is therefore necessary that the output gear should stop in such an angular position that, on reestablishment of the current in the ancillary power supply circuits, the automatic electric re-winding means will be in a condition to operate. Thus, in particular, where the re-winding means is controlled by means of a switch, it is necessary that the switch contacts are closed in said position.

A spring-drum assembly of the type here referred to includes rotatable annular drum gear and an output gear mounted coaxially, and a spiral hairspring having its outer end attached to the drum gear and its inner end attached to the hub of the output gear. A re-winding process involves rotating the drum gear with respect to the output gear in the same direction as the normal direction of rotation of the output gear and at a greater angular rate, so as to wind up and store energy in the hairspring. The torque transmitted from the hairspring to the output gear depends on the angle by which the drum has been rotated with respect to the output gear. If the hairspring is completely unwound or relaxed, the torque is of course zero. Asthe angle of rotation of the drum relative to the output gear is increased, the torque first increases and thereafter retains a substantially constant value. When the hairspring has been completely wound up with its turns touching one another, the torque becomes equal to the torque applied to the drum, and hence sustains a sudden step increase.

In order to ensure that the escapement shall operate under a substantially constant torque, it is customary to interpose, on assembly, suitable stops between the drum gear and the output gear, after first having wound up the hairspring so that it will urge the drum and output gear into a relative position in which said stops are in engagement, with the value of the torque operative at this time being well within its constant range, that is, being placed on the horizontal leg of the curve plotting the variations of torque as a function of angular displacement. This value is so selected that the maximum winding-up angle authorized by the electrical re-winding means will still correspond to said horizontal leg of the curve. In these conditions a substantially constant torque is available at that escapement wheel and a regular reciprocation of the balance wheel is ensured.

In a system according to the present invention, the re-winding process is performed, as known per se, by an electric motor driving a worm on its output shaft meshing with a worm-gear coaxially secured to the drum gear, and placed under control of a switch which is actuated to closed position by the output gear and is actuated to open position by the drum.

The requisite automaticity of the re-winding operations is provided for by placing the motor under the control of torque variations. Specifically, .a re-wind is initiated whenever the available energy in the hairspring has dropped to a prescribed minimum level, and the rewinding motor is disabled too soon as the stored energy in the hairspring has attained a prescribed maximum.

In view of the cyclic character of the re-wind process and in order to simplify the mechanism, matters are preferably so arranged that each re-wind step involves substantially one single revolution, the hairspring being constructed to have appropriate characteristics for such purpose.

Since the voltage output of the storage battery varies greatly as earlier indicated, it is necessary that the motor shall have sufiicient power to impart the one-revolution rotation to the drum at minimum voltage conditions. When on the other hand the battery is delivering maximum voltage, the action of the motor would be extremely fast, and it then is necessary to allow the inertia of the motor and the drum to exhaust itself when the switch is opened on completion of the revolution.

From the foregoing it will be evident that with the system of the invention, at minimum battery voltage conditions, the re-winding process will stop practically instantaneously as soon as the motor switch is opened, i.e. after one revolution, whereas with maximum battery voltage, the drum gear may, under inertia, elfect nearly one full additional revolution after the motor switch has opened.

Furthermore, the switch is always closed when the hairspring has been disabled due to engagement of the stops on the drum and output gear after the current in the ancillary power supply circuit has been cut off.

Moreover, the system is so arranged that the re-wind control switch closes prior to engagement between the stops on the drum and the output gear, whereby the output gear will still possess suflicient energy to ensure effective closure of the switch.

An exemplary embodiment of the invention will now be disclosed in detail for purposes of illustration but not of limitation with reference to the accompanying drawings, wherein:

FIGURE 1 is an overhead plan view of a re-winding system according to the invention, with its upper cover plate removed.

FIGURE 2 is a partial sectional view on line 11-11 of FIGURE 1.

FIGURE 3 is a partial view as seen on the arrow III of FIGURE 1 illustrating the switch-actuating clamp jaw device; and

FIGURE 4 is a partial schematic view illustrating the various components of the spring-drum assembly in mounting position.

In the illustrated embodiment, there is provided a tachometer clockwork mechanism including a springdrum assembly having an annular drum gear 1 secured on a shaft 2 rotatably mounted across a pair of parallel spaced plates 3 and 4, held in assembled relation by means of spacer rods such as 5. The spring-drum assembly further includes the output gear 6 rotatably mounted on shaft 2 and a spiral hairspring 8 has its inner end attached to a hub element 7 of the output gear 6 and its outer end attached to the rim of drum gear 1 (see FIG- URE 2).

Mounted around the shaft 2 over the output gear 6 is a dished spring washer 9 followed by a cam 10 followed 'in turn by a driver member 11 having a radially projecting driver arm 14. The driver member 11 is secured to shaft 2 by a cotter pin 12 so as to be rotatable bodily with the drum gear 1 of the spring-drum.

The cam member 10 is sector-shaped, and is provided at one side thereof directed away from output gear 6, and over part of its angular extent, the right end part as seen in FIGURES 1 and 4, with a projecting boss portion 13 adapted to cooperate with the driver arm 14 through engagement of said arm with either of the radial end wall surfaces of the boss 13. The cam member 10 is formed, on the side thereof directed towards the output gear 6,

-With.an arcuate groove 15 into which a pin 16 projecting from output gear 6 can project. Groove 15 terminates in the radial end wall of cam 10 remote from boss 13.

The drum 1 has a pin 17 projecting from its side remote from the output gear 6 and positioned substantially in the same radial plane as that of the driver arm 14 of driver member 11. It will thus be seen that the output gear 6 is relatively rotatable with respect to the drum 1 over an angular range which is limited at one end by a run-down position shown in FIGURE 4 in which the left-hand radial end wall 18 (as in FIGURES 1 and 4) of camming boss 13 engages the arm 14 of driver 11, with the pin 16 of output gear 6 simultaneously engaging the opposite or right-hand end wall 19 of the camming boss,

and a (theoretical) fully wound-up position wherein the right-hand end wall 19 of the cam boss engages the driver arm 14 while the stop pin 16 of output gear 6 is engaging the inner end wall of groove 15 thereby blocking the output gear 6.

The drum 1 has a peripheral set of gear teeth 21 adapted to mesh with the thread of a worm 22 secured on the output shaft of a small electric motor 23 mounted on a bracket 20 secured to plate 3. Owing to the irreversible character of the gearing provided by the worm 22 and the gear teeth 21, the drum 1 is blocked in a stationary condition so long as the motor is stationary. The motor 23 when energized rotates in a direction such that worm 22 will rotate the drum 1 in the same direction as the direction in which the output gear 6 is rotated in operation, that is counterclockwise according to the drawings as indicated by arrow F.

The starting and stopping of the motor 23 is controlled by a quick-opening switch 26 consisting of a pair of spring contact strips 24, 25. The spring strips are mounted on the supporting bracket 20 by means of screws 27 extending through insulator sleeves 28, with the interpos-al of insulating spacer shims 29 and 30. In the normal or idle condition of the switch thus constructed, the contacts 26 of strips 24 and 25 are not in engagement and the switch is open. The spring strips 24, 25 are electrically connected as shown in FIGURE 1 in the energizing circuit for motor 23.

The means for actuating the switch 26 to closed condition comprises a clamp-like device including a pair of jaw members 33 and 34 pivoted about a common pivot 35 supported across the plates 3 and 4 in a direction parallel to the main shaft 2 of the spring barrel assembly. The jaw members 33 and 34 have inturned lower ends to which are secured, e.g. riveted, actuator strips 32 of insulating material adapted to act with their inner edges upon the outer sides of the respective contact strips 24 and 25. The outer one 33 of the jaw members is provided with an extension 36 which is arranged to project at an angle into the path of the pin 17 of drum annulus 1. The jaw member 33 is urged in a counterclockwise direction (in FIGURE 1) about its pivot 35 so that 1ts outer side engages a stop 37 provided on plate 3, by a suitable spring action which in this embodiment is developed by the spring contact strip 24.

The other or inner jaw member 34 is provided with a radial arm 38 formed at its outer end with a bent-out lug portion 39 (see FIGURE 3) projecting beyond the plane of the output gear 6 and adapted to engage into a notch 40 formed in one, 41 of the arms of a two-armed pawl 42 pivoted on a pivot 43 of plate 4. A tension spring 44 having its ends attached to lugs 45 and 46 projecting from arm 38 and pawl 42 respectively, tends to draw the lug 39 towards the pivot 43 of the pawl so as to rotate the jaw member 34 counterclockwise into engagement with the contact strip 25.

The other armof pawl 42 has a tooth 47 which in the idle condition of the assembly with lug 39 engaging notch 40, is interposed in the path of the outer peripheral surface 48 of segmental cam 10. The amplitude of radial displacement of tooth 47 by the action of the cam is such that, when the tooth is urged outwardly by the said peripheral edge 48 of the cam, the lug 39 -is caused to disengage the notch 40, whereby the clamp device 32-34 is urged to its closed position shown in FIGURE 1, in which the contacts 26 are in engagement.

The system described operates as follows:

In the wound-up condition of the movement, the stop pin 17 of drum 1 has moved beyond the extension 36 of clamp jaw 33. The clamp 32 is in open condition, and lug 39 is engaged in notch 40. The cam 10 has rotated sufliciently so that its periphery 48 is no longer engaging the tooth 47 of pawl 42. The switch contacts 26 are open and the motor 23 is deenergized. The drum 1 is stationary.

The output gear 6 is revolving at the prescribed rate as determined by conventional escapement mechanism, not shown, forming part of the clockwork movement.

When the output gear 6 has rotated a predetermined angular amount, the pin 16 thereof engages the rear radial edge 19 of the cam boss 13, whereupon the cam is driven in rotation with the gear 6. The dished spring washer 9 serves to apply the cam 10 under slight axial force against the driver '11 and thus to prevent frictional entrainment of the cam with the gear 6.

- As the outer periphery 48 of cam 10 engages the tooth 47 of pawl 42, pivoting the pawl counterclockwise about its pivot 43, the log 39 is released from out of notch :40 as previously described and the tension spring 44 causes the clamp jaw 34 to rotate inthe counterclockwise direction indicated by arrow f, and since the clamp jaw 33 is abutted against the stop 37, the insulator elernents 32 cooperate to move the contact strips 24, 25

to switch-closing position.

Closure of the switch contacts 26 energizes the motor 23, which then rotates worm 22 and hence rotates the drum 1 in the direction indicated by arrow F at an angular speed faster than that of the output gear 6, which meanwhile continues to revolve.

The drum 1 rotates until its stop pin 17 engages the extension 36 of clamp jaw 33, rotating the latter clockwise about its pivot. 35. The arm 14 of driver member 11 engages the side 19 of boss 13, rotating the cam at an increased rate in the direction of arrow F and releasing the pawl 42.

The clockwise rotation of clamp jaw 33 about pivot 35 acts to rotate the whole assembly of strips 24, 25 and .clamp jaw 34 bodily clockwise, with switch contacts 26 instantaneously as the pin 17 moves beyond the extension 36 of clamp jaw 33 and thereby opens the switch contacts 26 as just described.

If on the other hand the motor supply voltage is high, the rotational velocity of the motor is high and its inertia combined with that of the drum 1 are then so high that the drum may rotate by a large additional angle after the contacts 26 have opened before actually stopping. To

' take care 'of this possibility, the sector cam 10 is provvided with an angular extent so small that, after the drum 1 has stopped, the cam will not be rotated into engagement with the tooth 47 of the pawl 42 by the action of driver arm 14 on boss 13. Moreover, both the cam 10 and drum 1 are preferably made of lightweight material such as a synthetic resin to reduce inertia and prevent the cam being propelled'towards the pawl by driver arm 14. The spring washer 9 further serves to retard the rotation of cam 10 under the momentum of the moving parts.

Should the power supply to the motor be cut off before the cam 10 has engaged the pawl 42 and thus produced the re-winding action, the clockwork movement continues to operate. The output gear 6 continues to rotate in the direction of arrow F. The pin 16 acts on the wall 19 of the cam and drives the cam in rotation. The cam deflects pawl 42, closing the contacts 26. This closure of the switch contacts is ineffective since the motor power supply is at this time out off. The drum 1 therefore remains stationary. The output gear 6 continues to revolve until the cam 10 has been urged by pin 16 into engagement with the arm 14 of driver 11 which is fixed for rotation with the drum 1, as in the position shown in FIGURE 4. The clockwork movement then steps but, since the con- The motor 23 is deenergized and its ro-.

6 tacts 26 are closed, a re-winding action will be performed as soon as the power is reapplied, as earlier explained,

It may happen that, at the instant power is reapplied, the voltage output from the storage battery is very low, so that the motor drives the drum 1 at a velocity so slow that it is in effect followed by the cam 10 as the latter is rotated by the action of pin 16 of the output gear 6. In these conditions the cam 10 will engage the tooth 47 of the pawl 42 before the pin 17 of the drum 1 has acted to deflect the extension 36 of clamp jaw 33. This will not produce any effect since the switch 26 is at such time closed; however, it is necessary that the cam boss 13 shall have an angular extent great enough to hold the tooth 47 in its radially outer position so long as the extension 36 has not escaped from the action of stop pin 17. Otherwise, the clamp jaw 33 would lock the clamp jaw 34 against the arm 41 and the contacts would open, arresting the re-wind action while the output gear is being engaged by the driver arm 14 which is rotatable with the drum (FIGURE 4), and there would be no way of reinitiating the movement.

Since the output gear 6 is rotated by the energy stored in the hairspring 8 of the drum assembly and since the re-winding action is produced by the output gear 6 acting through its pin 16 on the cam 10 to release the clamp jaw 34 from the notch 40 in pawl 42, it is desirable that even under the least favorable conditions the cam 10 shall be capable of acting on the tooth 47 of pawl 42 before the hairspring has run down a substantial degree. The most unfavorable conditions are those occurring when the electric voltage output from the battery is low and the drum member 1 has stopped just after the stop pin 17 has passed beyond the extension 36 of clamp jaw 34. The active peripheral edge 48 'of cam 10 should therefore be long enough, in the part thereof extending beyond the boss 13, to ensure that in the drum position just noted, the cam surface 48 will act on the pawl tooth 47 at an instant well ahead of the time that the cam 10 and the output gear 6 have engaged the arm 14 of driver 11 and the hairspring has yielded up all of the energy stored in it in the preceding re-winding cycle.

When the assembly described is first mounted and with the power cut off, the various parts occupy the positions illustrated in FIGURE 4. That is, the stop pin 17 is positioned just beyond the extension 36, the boss 13 of cam 10 is in engagement with the arm 14 of the driver, and the pin 16 of output gear 6 is in engagement with the rear wall 19 of cam 10. The pawl 42 is shifted outward by the outer periphery of cam 10, jaw member 34 is disengaged and the switch contacts 26 are closed. In this condition of the components, a re-winding cycle will be initiated so soon as the electric power is applied.

It will be understood that various modifications may be introduced into the single form of embodiment of the invention illustrated and described herein Without exceeding the scope of the invention as defined in the appended claims.

What I claim is:

1. Clockwork mechanism provided with automatic rewinding means comprising in combination: a spring drum assembly including a drum, an output gear coaxial with and rotatable relative to the drum and a hairspring having ends attached to the drum and output gear respectively for rotating the output gear; a re-winding electric motor geared for rotating the drum at a rate which is normally faster than the rate of rotation of the output gear; an energizing circuit for the motor; switch contacts connected in said circuit; and contact-operating means comprising a clamping device displaceable between an open position permitting opening of the contacts and a clamped position effecting closure of the contacts; a cam coaxial with and rotatable relative to said drum and output gear; means rotatable with the output gear engageable at a point in the rotation thereof with said cam to rotate the cam with the output gear; latching means operable to latch the clamping device in said open position and cammingly engageable by the cam during rotation thereof so as to be displaced to a releasing position permitting contact closure whereby said motor is energized and said drum is rotated at said normally faster rate on a re-winding cycle; means rotatable with the drum and engageable during rotation thereof with said clamping device to displace it to open position to permit contact opening for deenergizing the rotor and arresting the drum to terminate the re-winding cycle; and means rotatable with the drum and engageable during rotation thereof with the cam to rotate the cam at said normally 'faster rate for disengaging said latching means whereby said clamping device is latched in said open position.

2. The mechanism defined in claim 1, wherein said switch contacts comprise a pair of spring strips normally biassed to an open condition, and said clamping device comprises a pair of interpivoted jaw members engage- .able with the outer sides of the strips in said clamped position of the device.

3. The mechanism defined in claim 2, wherein said latching means comprises a pivoted pawl having a part engageable by said cam and a latching part engageable with one of said jaw members to latch the latter, and said first means rotatable with the drum is engageable with the other jaw member to open the clamping device when said one jaw member is latched by said latching part of the pawl.

4. The mechanism defined in claim 2, wherein said second-mentioned means rotatable with the drum is engageable with one of two oppositely-directed radial surfaces of the cam when the drum is rotated at said normally faster rate, and with the other of said oppositelydirected radial surfaces when the drum is rotated at a slower or a zero rate of rotation.

5. The mechanism defined in claim 2, wherein said drum and cam are made of lightweight synthetic resin material.

6'. Clockwork mechanism provided with automatic rewinding means, comprising in combination: a spring drum assembly including a drum, an output gear coaxial with and rotatable relative to the drum and a hairspring having ends attached to the drum and output gear for rotating the output gear at a prescribed rate; a re-winding electric motor geared for rotating the drum at a rate which is normally faster than said prescribed rate during a re-winding cycle; an energizing circuit for the motor; switch contacts connected in said circuit; means spring-urging the contacts to open condition to deenergize the motor; and contact-operating means comprising a clamping device displaceable between an open position disengaging the contacts to permit opening thereof and a closed position engaging the contacts to close them; means urging the clamping device to said closed position; a latching member movable between a latching position in engagement with the clamping device to latch it in said open position and a releasing position permitting displacement of the clamping device to closed position; means urging the latching member to latching position; a sector cam mounted for coaxial rotation relative to the drum and output gear; means rotatable with the output gear and circumferentially engageable at a point in the rotation thereof with a radial surface of the cam to rtate the cam with the output gear; said cam having an arcuate sector periphery radially engageable with said latching member to move same to said releasing position to permit displacement of the clamping device to closed position and permit contact closure to start the motor and rotate the drum on a rewinding cycle at said normally faster rate; means rotatable with the drum and circumferentially engageable with said radial cam surface to rotate the cam at said normally faster rate whereby the cam periphery will disengage the latching member and allow it to be moved to said latching position; and means rotatable with the drum and engageable with said clamping device to displace it to said open position to be latched thereat by said latching member, and to permit opening of the contacts to deenergize the motor and arrest the drum to terminate. the re-winding cycle.

7. The mechanism defined in claim 6, wherein said switch contacts comprise a pair of spring strips normally biassed to an open condition, said clamping device comprises a pair of inter-pivoted jaw members engageable with the outer sides of the strips in said clamped position of the device, said latching means comprises a pivoted pawl having a camming part engageable by said cam periphery and a latching part engageable with one of said jaw members to latch the latter, and said second means rotatable with the drum is engageable with the other jaw member to open the clamping device when said one jaw member is latched by said latching, part of the pawl.

8. The mechanism defined in claim 6, wherein said sector cam has two-oppositely-directed radial surfaces one of which is engageable by said first-mentioned means rotatable with the drum when the drum is rotated at said normally faster rate and the other when the drum is rotated at a slower or a zero rate.

9. The mechanism defined in claim 7, wherein said second means is a pin projecting axially from the drum and said other jaw member has an extension engageable by said pin for first .bodily rocking said clamping device with said contacts clamped therebetween in closed condition until said one jaw member is latched by said latching part, and thereafter diseng ageable by said pin to allow said other jaw member to spring back and effect a rapid opening of the contacts.

10. The mechanism defined in claim 9, wherein the circumferential dimensioning of the cam parts is such that the arcuate cam periphery is still engaging said camming part of the pawl when the other of said radial cam surfaces is engaging said first-mentioned means rotatable with the drum and said pin has disengaged said one jaw member.

11. The mechanism defined in claim 10, wherein said circumferential dimensioning is further such that said cam periphery engages said latching member to start the re-winding motor substantially before the hairspring has been unwound to a relaxed condition.

12. The mechanism defined in claim 9, wherein said sector cam has an arcuate slot extending from a radial end surface thereof remote from said first-mentioned radial surface and said pin is freely projectable into said slot for increasing the range of relative rotation between the drum and the output gear.

References Cited by the Examiner UNITED STATES PATENTS 5/1931 Fowler -40 5/ 1941 Flegel 200-39 

1. CLOCKWORK MECHANISM PROVIDED WITH AUTOMATIC REWINDING MEANS COMPRISING IN COMBINATION: A SPRING DRUM ASSEMBLY INCLUDING A DRUM, AN OUTPUT GEAR RESPECAND ROTATABLE RELATIVE TO THE DRUM AND A HAIRSPRING HAVING ENDS ATTACHED TO THE DRUM AND OUTPUT GEAR RESPECTIVELY FOR ROTATING THE OUTPUT GEAR; A RE-WINDING ELECTRIC MOTOR GEARED FOR ROTATING THE DRUM AT A RATE WHICH IS NORMALLY FASTER THAN THE RATE OF ROTATION OF THE OUTPUT GEAR; AN ENERGIZING CIRCUIT FOR THE MOTOR; SWITCH CONTACTS CONNECTED IN SAID CIRCUIT; AND CONTACT-OPERATING MEANS COMPRISING A CLAMPING DEVICE DISPLACEABLE BETWEEN AN OPEN POSITION PERMITTING OPENING OF THE CONTACTS AND A CLAMPED POSITION EFFECTING CLOSURE OF THE CONTACTS; A CAM COAXIAL WITH AND ROTATABLE RELATIVE TO SAID DRUM AND OUTPUT GEAR; MEANS ROTATABLE WITH THE OUTPUT GEAR ENGAGEABLE AT A POINT IN THE ROTATION THEREOF WITH SAID CAM TO ROTATE THE CAM WITH THE OUTPUT GEAR; LATCHING MEANS OPERABLE TO LATCH THE CLAMPING DEVICE IN SAID OPEN POSITION AND CAMMINGLY ENGAGEABLE BY THE CAM DURING ROTATION THEREOF SO AS TO BE DISPLACED TO A RELEASING POSITION PERMITTING CONTACT CLOSURE WHEREBY SAID MOTOR IS ENERGIZED AND SAID DRUM IS ROTATED AT SAID NORMALLY FASTER RATE ON A RE-WINDING CYCLE; MEANS ROTATABLE WITH THE DRUM AND ENGAGEABLE DURING ROTATION THEREOF WITH SAID CLAMPING DEVICE TO DISPLACE IT TO OPEN POSITION TO PERMIT CONTACT OPENING FOR DEENERGIZING THE ROTOR AND ARRESTING THE DRUM TO TERMINATE THE RE-WINDING CYCLE; AND MEANS ROTATABLE WITH THE DRUM AND ENGAGEABLE DURING ROTATION THEREOF WITH THE CAM TO ROTATE THE CAM AT SAID NORMALLY FASTER RATE FOR DISENGAGING SAID LATCHING MEANS WHEREBY SAID CLAMPING DEVICE IS LATCHED IN SAID OPEN POSITION. 